• Nigeria has the highest burden of Lassa fever cases in West Africa.
• Strengthening of capacity for laboratory diagnostics and case management in previous years resulted in greater case detection.
• Major LF outbreaks reported in since 2018, with 5344 confirmed cases since 2020.

• Lassa fever cases in Nigeria by week show a seasonal effect: the number of cases peaks during the dry season period (from epi week 47 - week 12).
• The seasonal increase of cases during the dry period may be attributed to an increase of the infected rodent population and/or a seasonal behavioural change in the human population resulting in a higher risk of exposure to infected animals and/or to food/household items contaminated with rodent excreta.

From January 2018 to December 2024, 75% of Lassa fever confirmed cases were from Ondo (33%), Edo (31%) and Bauchi (11%).

• Total suspected cases: 38,754
• Total confirmed cases: 5,879
• Deaths from Confirmed Cases: 1,076
• Case Fatality Ratio: 20%
• Number of Health Care Workers: 229

• From 2017-2024, a total of 36,022 suspected cases were reported from 26 in Zamfara to 13,950 in Edo.

• From 2017-2024, CFR among all laboratory confirmed cases in Nigeria was between 16-27% and decreased over the years.
• In 2024, overall CFR for Nigeria was 16% and differed greatly by individual State.
• In general, variation of CFR is likely due to late presentation of patients and differences in case management which may indicate a need for improvement.

• From 2020-2024, a total of 212 healthcare workers (HCW) were reported among confirmed cases, that is 4% of Lassa fever cases.
• From 2020-2024, 60% of all HCW infections were from Ondo (26%), Bauchi (20%), Edo (15%) States where 75% of all Lassa fever patients were being cared for. 12% of HCW infections are reported from Ebonyi where 6% of Lassa fever patients were being cared for.
• Higher proportion of HCW in States with low incidence (10-30%).

• In 2025, a total of 2,732 suspected cases were reported from 1 in Niger, Akwa Ibom, Jigawa, Yobe to 866 in Edo.

• Nigeria has the highest burden of Lassa fever cases in West Africa.
• Strengthening of capacity for laboratory diagnostics and case management in previous years resulted in greater case detection.
• Major LF outbreaks reported in since 2018, with 5344 confirmed cases since 2020.

• In 2025, similar trend as per previous years confirming a seasonal effect on Lassa fever incidence.
• Compared to 2024, 22% decrease in the cumulative number of confirmed cases reported.

• In 2025, as of epi week 9, 88% of LF cases are from Ondo (31%), Bauchi (24%), Edo (17%), and Taraba (16%) States.

• Total confirmed cases: 535

• Deaths from Confirmed Cases: 100

• Case Fatality Ratio: 19%

• Number of Health Care Workers: 17

• As of epi week 9 2025, cumulatively 535 cases and 100 deaths (CFR=19%) across 13 States have been reported
• At same period 2024, a total of 27 States reported at least one confirmed cases.
• There is a 30% decrease in the number of suspected cases reported in 2025 compared to 2024.
• In 2024, 34 States had reported at least one suspected case versus 31 in 2025 to date.

• As of epi week 9 of 2025, there has been 17 healthcare workers infected, that is 3% of confirmed cases.
• 8 HCW infections in Ondo, 4 in Bauchi, 2 in Gombe, 1 in Edo and 2 in Taraba.

• As of week 9, 2025, Ondo State reported 1947 confirmed cases including 282 deaths (CFR 14%).
• In 2025 only, Ondo State reported 168 confirmed cases including 21 deaths (CFR 12%).
• Compared to same period 2024, this represents a 9% increase in the number of confirmed cases and a 75% increase in CFR.

• As of week 9, 2025, Bauchi State reported 811 confirmed cases including 157 deaths (CFR 19%).
• In 2025 only, Bauchi State reported 128 confirmed cases including 10 deaths (CFR 8%).
• Compared to same period 2024, this represents a 24% increase in the number of confirmed cases and a 66% decrease in CFR.

• As of week 9, 2025, Edo State reported 1601 confirmed cases including 179 deaths (CFR 11%).
• In 2025 only, Edo State reported 93 confirmed cases including 15 deaths (CFR 16%).
• Compared to same period 2024, this represents a 43% decrease in the number of confirmed cases and a 26% increase in CFR.

• As of week 9, 2025, Taraba State reported 414 confirmed cases including 130 deaths (CFR 31%).
• In 2025 only, Taraba State reported 83 confirmed cases including 26 deaths (CFR 31%).
• Compared to same period 2024, this represents a 11% increase in the number of confirmed cases and a 38% increase in CFR.

• As of week 9, 2025, Ebonyi State reported 272 confirmed cases including 120 deaths (CFR 44%).
• In 2025 only, Ebonyi State reported 17 confirmed cases including 8 deaths (CFR 47%).
• Compared to same period 2024, this represents a 55% decrease in the number of confirmed cases and a 6% decrease in CFR.

• As of week 9, 2025, Kogi State reported 154 confirmed cases including 26 deaths (CFR 17%).
• In 2025 only, Kogi State reported 14 confirmed cases including 4 deaths (CFR 29%).
• Compared to same period 2024, this represents a 48% decrease in the number of confirmed cases and a 671% increase in CFR.

• As of week 9, 2025, Gombe State reported 59 confirmed cases including 21 deaths (CFR 36%).
• In 2025 only, Gombe State reported 11 confirmed cases including 6 deaths (CFR 55%).
• Compared to same period 2024, this represents a 267% increase in the number of confirmed cases and a 64% increase in CFR.

• As of week 9, 2025, Benue State reported 166 confirmed cases including 34 deaths (CFR 20%).
• In 2025 only, Benue State reported 5 confirmed cases including 3 deaths (CFR 60%).
• Compared to same period 2024, this represents a 90% decrease in the number of confirmed cases and a 247% increase in CFR.